The preferential in vitro methylation of histone H3 by coactivator-associated arginine methyltransferase 1 (CARM1) has been proposed as a basis for its ability to enhance gene transcription [Chen, D., et al. (1999) Science 284, 2174-2177]. To further evaluate the significance of H3 methylation, we studied the kinetics and site specificity of its modification by CARM1. Affinity-purified CARM1 methylated recombinant chick H3, which is free of posttranslational modifications, and calf thymus H3, which is heterogeneous with regard to preexisting modifications, equally well, exhibiting a V(max) of 4500 pmol min(-1) (mg of enzyme)(-1) and an apparent K(m) for H3 of < or = 0.2 microM. The catalytic efficiency (k(cat)/K(m)) of CARM1 toward H3 was at least 1000 times that toward R1 (GGFGGRGGFGG-amide), a highly effective substrate for protein arginine methyltransferase 1. Peptide mapping of 3H-methyl-labeled H3 indicated methylation at Arg-2, Arg-17, and Arg-26 in the N-terminal region and at one or more of four arginines (128/129/131/134) at the C-terminus. Two of the N-terminal sites, Arg-17 and Arg-26, occur in the sequence KAXRK and appear to be more efficiently methylated than Arg-2. CARM1 catalyzed formation of N(G),N(G)-dimethylarginine (asymmetric) but little or no N(G),N'(G)-dimethylarginine (symmetric) and no form of methyllysine. Amino acid analysis of untreated calf thymus H3 revealed that 3.7% of the molecules naturally contain asymmetric dimethylarginine and/or monomethylarginine. Our findings support the hypothesis that methylation of H3 may be involved in the mechanism of transcriptional coactivation by CARM1 of genes whose expression is under the control of nuclear receptors.

Breast implant-associated anaplastic large cell lymphoma is a rare cancer in patients with breast implants but is increasing in incidence. It is important for all physicians involved in the care of patients with breast implants to be aware of this entity and be able to recognize initial symptoms.

The Robin sequence, previously known as the Pierre Robin syndrome, is characterized by the sequence of clinical events that result from a small mandible. The tongue becomes posteriorly displaced (glossoptosis) and obstructs the airway. The obstructing tongue also makes oral feeding difficult and, in severe cases, impossible. Patients with Robin sequence may also present with a cleft palate, although this is not necessary to make the diagnosis. The small mandible either results from an inherent growth problem (genetic or syndromic) or is deformational where intrauterine growth of the mandible is restricted. Conditions of syndromic patients are generally more severe and difficult to treat. The phenomenon of "catch-up" growth is disputed, although it is likely to occur in deformational but not syndromic patients. Patients with Robin sequence are best managed by a multidisciplinary team familiar with the diagnoses and treatment of difficult pediatric airways. Approximately 70% of Robin infants are successfully managed by prone positioning alone. Tracheostomy is necessary in approximately 10% of these patients, especially for subglottic obstructions including laryngomalacia and tracheomalacia. Tracheostomy should be avoided if possible. Treatment of the remaining 20% remains highly contentious. Tongue-lip adhesion, nasopharyngeal airways, and distraction osteogenesis all have strong advocates. Ideally, treatment should be individualized. Patients who will have catch-up growth of the mandible will only need a tongue-lip or nasopharyngeal airway as a temporary measure. Patients who we know will not have catch-up growth will benefit from early distraction osteogenesis.